The Cost of Digital Advertisement: Comparing User and Advertiser Views Panagiotis Papadopoulos Nicolas Kourtellis Evangelos P. Markatos FORTH-ICS, Greece Telefonica Research, Spain FORTH-ICS, Greece [email protected] [email protected] [email protected] ABSTRACT vast majority of the content providers offer their websites or their Digital advertisements are delivered in the form of static images, sophisticated services free-of-charge (e.g. Google Docs, Facebook, animations or videos, with the goal to promote a product, a service Twitter, Gmail) in exchange for allowing third parties to access and or an idea to desktop or mobile users. Thus, the advertiser pays a display advertisements to their users. monetary cost to buy ad-space in a content provider’s medium (e.g., Online advertising progressively moves towards more personal- website) to place their advertisement in the consumer’s display. ized ad delivery through a programmatic ad-buying model. In this However, is it only the advertiser who pays for the ad delivery? model, advertisers buy available ad-slots in the user’s display in Unlike traditional advertisements in mediums such as newspa- an automated fashion based on how well the advertised product pers, TV or radio, in the digital world, the end-users are also paying matches the profile of the user. As a consequence, when a user visits a cost for the advertisement delivery. Whilst the cost on the adver- a website, each of the available ad-slots is auctioned, and advertisers tiser’s side is clearly monetary, on the end-user, it includes both decide if they will bid and how much, based on the information quantifiable costs, such as network requests and transferred bytes, (interests, income, gender etc.) they have about the current user. and qualitative costs such as privacy loss to the ad ecosystem. Following the above process, a careful reader identifies 3 key role In this study, we aim to increase user awareness regarding the players: (i) the website provider who earns money from advertisers hidden costs of digital advertisement in mobile devices, and com- through the auctions, (ii) the advertisers that pay to promote, and pare the user and advertiser views. Specifically, we built Open- eventually sell their products by delivering effective advertisements DAMP, a transparency tool that passively analyzes users’ web traf- to the proper eyeballs, and (iii) the user that receives from the fic and estimates the costs in both sides. We use a year-long dataset website the content of his interest, for free. Seemingly, everyone of 1270 real mobile users and by juxtaposing the costs of both sides, benefits from this model. But are the users indeed receiving the we identify a clear imbalance: the advertisers pay several times less content they want free of charge? to deliver ads, than the cost paid by the users to download them. Contrary to the traditional advertising (i.e. in newspapers, TV, In addition, the majority of users experience a significant privacy radio), in the digital world, it is not only the advertiser that pays the loss, through the personalized ad delivery mechanics. cost of advertisement delivery, but the user as well! Indeed, it is the user’s data plan that is being charged to download the additional CCS CONCEPTS ad-related KBytes. To make matters worse, there are several other bytes the user downloads regarding analytics and user tracking, • Information systems → Online advertising; Web log analy- totally unassociated with the actual content of the visited website. sis; • Security and privacy → Economics of security and privacy; Of course, the cost is not only monetary, since the privacy loss of KEYWORDS the above operation has proven significant [33, 44]. In this study, we examine the hidden costs of mobile advertising Cost of mobile advertising, Personalized advertising, User privacy for both the transmitter (advertiser), and the receiver (user) of the ACM Reference Format: advertisments. In fact, we compare them for the same user profiles Panagiotis Papadopoulos, Nicolas Kourtellis, and Evangelos P. Markatos. and investigate how fairly they are shared among the two sides. Our 2018. The Cost of Digital Advertisement: Comparing User and Advertiser motivation is to enhance transparency regarding the overall costs Views. In WWW 2018: The 2018 Web Conference, April 23–27, 2018, Lyon, of online advertising, and increase awareness of users regarding France. ACM, New York, NY, USA, 11 pages. https://doi.org/https://doi.org/ hidden costs they pay while using ad-supported online services. 10.1145/3178876.3186060 Past works in the area already attempted to reveal the hidden 1 INTRODUCTION costs of advertising in the mobile ecosystem. For example, Gui et al. [25] analyze free and paid version of apps to compare the ad- The digital advertising business grew to $194.6 billion in 2016 [51] vertising costs from the developers’ side. They actively analyzed of which $108 billion were due to mobile advertising. In addition, mobile apps to measure costs related to memory, power consump- it is digital advertising that fuels the internet as we know it. The tion and CPU usage. Similar to the study of Gao et al. [20], they This paper is published under the Creative Commons Attribution 4.0 International compared these costs with the users’ feedback from app reviews. (CC BY 4.0) license. Authors reserve their rights to disseminate the work on their This work is the first to our knowledge that measures the hidden personal and corporate Web sites with the appropriate attribution. cost of advertising when mobile users browse the web. Contrary WWW 2018, April 23–27, 2018, Lyon, France to the above inspiring approaches, our more user-centric study © 2018 IW3C2 (International World Wide Web Conference Committee), published under Creative Commons CC BY 4.0 License. attempts to examine these costs, not from a developer perspective ACM ISBN 978-1-4503-5639-8/18/04. but from the side of the end-user. Towards this goal, we design a https://doi.org/https://doi.org/10.1145/3178876.3186060 Browser: methodology and we implement it in OpenDAMP: a tool to estimate tracker.com the costs of advertising for both advertisers and users, by passively cnn.com (1) GET tracker.com/beacon.gif Cookie: {cookie_ID=user123} analyzing a dataset of user HTTP traffic. We collected a dataset consisting of mobile traffic from 1270 volunteering users that spans over an entire year, and use OpenDAMP to analyze it. Finally, we compare the costs of both sides to assess how fair they are shared across the two ends. advertiser.com In summary, this work makes the following contributions: (3) GET (1) We design a methodology to measure the costs a user pays advertiser.com?syncID=user123&publisher=cnn.com when receiving ad-related traffic. These costs may be ei- Cookie: {cookie_ID=userABC} ther directly quantifiable (e.g., requests, bytes, energy), or qualitative such as loss of privacy. In addition, and building Figure 1: The CSync process in the wild. Two entities, through the user’s on previous approach [45], our methodology estimates the browser, match the IDs they have set for the particular user. costs advertisers pay to display each of the advertisements a Cookie Synchronization user receives through the contemporary programmatic RTB In order for all this abundance of user data to be useful for the auctions [56]. companies, there must be a matching process of all the userIDs (2) We implement our methodology in OpenDAMP (open Dig- that the third parties have assigned to the same user. By the notion ital Advertising Measurement Platform): a framework for userIDs, we define a string able to uniquely identify a user inthe passive weblog analysis oriented to digital advertising. Open- online world. In the web, the userID is an ID set on the user’s side DAMP can analyze user HTTP traffic and detect ID sharing typically in the form of a cookie (i.e. cookie ID). Cookies, however, incidents among third parties (known as Cookie Synchro- are domain-specific, which means those created by one third-party nizations). In addition, by incorporating information from entity cannot be read by anyone else (see same origin policy [54]). external resources and blacklists, OpenDAMP can classify To remedy this, Cookie Synchronization (CSync) [1, 21, 34, 42] was the traffic based on the content the domains deliver, and invented, with which third parties are able to match the different extract metadata and charge prices from RTB ad-auctions. userIDs they have set for the same user. Figure 1 presents a simple example to understand in practice how Cookie Synchronization (3) To assess the effectiveness of our methodology, we collected works. Let’s assume (i) a web site (say cnn.com), which includes a year-long dataset with mobile browsing traffic from 1270 some code from tracker.com and (ii) another third party site called volunteering users. Our analysis shows that the costs adver- advertiser.com, which is not included in the web page of cnn.com and tisers and users pay are largely unbalanced, In fact, users thus, does not (and cannot) know which users visit cnn.com. pay ∼3 times more through their data plan to download ads, Now, assume a user who, while browsing the web, got a cookie than what the advertisers pay to deliver them to these users. (cookieID=user123) by tracker.com, and another (cookieID=userABC) Furthermore, the majority of users sustains a significant loss by advertiser.com, and now visits cnn.com. As soon as the code of of privacy to receive these personalized advertisements. tracker.com is called, a GET request is issued by the browser to tracker.com (step 1). Then, tracker.com responds back with a redirect 2 COST ANALYSIS WITH OPENDAMP request (step 2), instructing the user’s browser to issue another GET In this study, we measure the hidden costs of advertising for users, request to advertiser.com, this time using a specifically crafted URL by passively monitoring their browsing traffic, while taking into (step 3): advertiser.com?syncID=user123&publisher=cnn.com along account the advertisers’ view.